You have some twin turbine helis with autopilot and LPV?
Emergency services may well be a use case.
This discussion is about LPV versus other GPS approaches. As such I lack experience to add something valuable to it, because I cannot tell whether the benefit of having LPV minimums tops much over any other approach type flown as CDA. What I see is that the cloud base can vary from one place to another. So it’s not exactly a question of safety in a SEP if you have say typically a cloud base of 1000 feet or more but just where that airport lies (quite sometimes on a hilltop) you have maybe only some hundred feet above the runway. That’s when an LPV could get handy.
I do see that several airfields here in Germany have set up an LPV approach or are in the process of setting it up. I can only make assumptions, but it looks like it was the same work involved to establish LPV or any other combination of VNAV or LNAV. And then obviously you go for the best approach type with lowest minimums.
I have an LPV approach quite close to my airfield that is exactly as I described before, it is some 600 feet higher than the surrounding and the DH is 250 feet.
UdoR wrote:
This discussion is about LPV versus other GPS approaches. As such I lack experience to add something valuable to it, because I cannot tell whether the benefit of having LPV minimums tops much over any other approach type flown as CDA.
For most light GA, LPV as such isn’t that important as you seldom fly is such hard IMC that you need LPV minima. On the other hand, having +V in the GPS box is important. AFAIK the capability to do LPV and +V go hand in hand.
UdoR wrote:
So it’s not exactly a question of safety in a SEP if you have say typically a cloud base of 1000 feet or more but just where that airport lies (quite sometimes on a hilltop) you have maybe only some hundred feet above the runway. That’s when an LPV could get handy.
If you have a cloud base of 1000ft or more you´re unlikely to benefit (added value) from LPV capability, since most (if not all) LNAV/VNAV approaches to the same runway will offer minima of 1000ft or less as well. In other words, no (or little) added value of LPV capability. Take a look at the majority of airports offering LPV approaches and you´ll find LNAV/VNAV approach availability as well. In general the RVR and DH differences between LPV and LNAV/VNAP approaches, at airfields with low minima LPV approaches (200-300FT), are like 100-200 meters RVR and 50-200FT height. Really not a big difference, considering possible equipment and installation costs vs utilization. In the commercial world – this could very well be worth it, but I don´t see it adding great value in the private pilot world.
The primary operational benefit of the LPV approach is the lower minima that you get from that (augmented) system, and this will mostly be to minima´s with less than 1000ft AGL (DH), just like the the non-LPV (LNAV/VNAV) approaches to the same runway.
Most GPS approaches (all but LNAV only) would be flown in coupled mode (if/when available) and only the LNAV approach would be flown as a CDA (due lack of vertical guidance).
Airborne_Again wrote:
AFAIK the capability to do LPV and +V go hand in hand.
I really am not very familiar with the “+V” concept, I need to investigate what that is, but the navigation requirements/ability to perform approach to LNAV/VNAV minima does for sure NOT require any augmentation (allowing for LPV/LP approaches), that is for sure.
Peter wrote:
ou have some twin turbine helis with autopilot and LPV?Emergency services may well be a use case.
It is. Hospital site. State primary level.
At La Rochelle LFBH LPV made it possible to add 2 further precision approaches. One being to 09 which didn’t have an IAP beforehand except for via a circle to land from the ILS or NDB approaches.
Now, there is an LPV approach to each runway. An ILS to 09 would have been too expensive. An non precision GNSS approach would have been possible, but the LPV was not a great deal more expensive in the overall scheme of things and much better value, it also allowing a back up for the ILS.
I have used the LPV to 09 on several occasions, returning on a winter’s night.
But they have all been in twins.
gallois wrote:
gallois14-Jan-24 16:2317
At La Rochelle LFBH LPV made it possible to add 2 further precision approaches. One being to 09 which didn’t have an IAP beforehand except for via a circle to land from the ILS or NDB approaches.
Now, there is an LPV approach to each runway. An ILS to 09 would have been too expensive. An non precision GNSS approach would have been possible, but the LPV was not a great deal more expensive in the overall scheme of things and much better value, it also allowing a back up for the ILS.
I have used the LPV to 09 on several occasions, returning on a winter’s night.
But they have all been in twins.
It´s not the LPV (augmentation GPS) that made the further approaches available at La Rochelle (or anywhere else!) as per se. The RNP Rwy 09 has the same minima for LPV and LNAV/VNAV (250ft/1300m), so the LPV added no value for the operator. The RNP Rwy 27 has a marginal lower minima for the LPV (200ft/750m) vs LNAV/VNAV (270ft/900m), it´s really marginal added value having the LPV capability.
One should not mix up, RNP with LPV, as they are two separate things, as you´ve also noted.
The (3D) LPV is a type of RNP (GPS) approach, and the (3D) LNAV/VNAV and (2D) LNAV are equally types of RNP (GPS) approaches. You don´t need an LPV certified (or capable) GPS system to perform the RNP approaches to LNAV/VNAV or LNAV minima.
The LNAV/VNAV approach (without LPV approach) would also have served as backup to the ILS, with slightly higher minima´s. I don´t think the LPV approach as a backup to the ILS adds any planning value/benefit when filing as an IFR destination airport.
The addition of the RNP Rwy 09 obviously adds overall value to the airport, since the wind factor now plays a lesser role and planning can be made based on these straight-in Rwy 09 minima´s (as opposed to the old circling only minima), but again the augmented LPV approach itself (as opposed to LNAV/VNAV) adds zero value, with the same minimas for both approaches.
If the question is what value the LPV capability of an aircraft adds, one must value the difference in minima´s and how frequently one would actually benefit from the slightly lower LPV minima´s.
Yeager wrote:
I really am not very familiar with the “+V” concept, I need to investigate what that is, but the navigation requirements/ability to perform approach to LNAV/VNAV minima does for sure NOT require any augmentation (allowing for LPV/LP approaches), that is for sure.
+V means that the GPS box generates an advisory glidepath for 2D approaches. AFAIK only SBAS boxes does that. Again, AFAIK, LNAV/VNAV also requires an SBAS box.
(To be precise, in neither of these cases is the augmentation really necessary, but they are not available on a non-SBAS box.)
Airborne_Again wrote:
+V means that the GPS box generates an advisory glidepath for 2D approaches. AFAIK only SBAS boxes does that. Again, AFAIK, LNAV/VNAV also requires an SBAS box.(To be precise, in neither of these cases is the augmentation really necessary, but they are not available on a non-SBAS box.)
Interesting. I have to admit again, that I was not aware that the aircraft GPS installation required an SBAS capable system in order to allow for an (3D) LNAV/VNAV approach to LNAV/VNAV minima.
I did have an “idea” that the aircraft GPS installation, with LPV ((WAAS)SBAS) capability, would be capable of producing a Vertical Glide Path for a (2D) LNAV (ONLY) approach and as such used for guidance, but ONLY to LNAV minima.
So, you´re saying that a non-WAAS(SBAS) GPS aircraft installation do not provide/display Vertical Guidance that can be legally used down to LNAV/VNAV minima´s? I´m not convinced, but could I´m uncertain.
EDIT (SORRY): A quick glance at some technical data discloses that you can indeed have non-WAAS(SBAS) GPS “boxes” and perform (3D) LNAV/VNAV approaches to applicable LNAV/VNAV minima, for as long as you have a barometric-VNAV system (which we do have on the more advanced jets (as well as SBAS of course). So, no, SBAS(WAAS) capable GPS “boxes” are NOT a requirement, as per se, to perform LNAV/VNAV approaches. SBAS capable GPS “boxes” is one way to allow for the Vertical Guidance for the LNAV/VNAV approach and ditto minima.
I need to look more into this. Thanks.
